1. Field of the Invention:
This invention relates to improvements in pipeline laying apparatus and more particularly, but not by way of limitation, to a marine trenching plow for excavating a pipeline trench in an underwater location while simultaneously laying the pipe in the dredge trench.
2. Description of the Prior Art:
It is common practice today to lay or bury marine pipelines on the floor of the ocean or other bodies of water to protect the pipeline from damage due to underwater currents, anchors, or other underwater hazards. The pipeline is normally carried on a lay barge and is wound onto and off of suitable reel means mounted on the barge whereby the pipeline is transferred to the ocean bottom. In addition, an underwater plow or trenching means is usually towed by the barge for dredging a pipeline receiving trench on the floor or bottom of the body of water. Conventional underwater trenching or marine dredging techniques frequently comprise the initial cutting of the trench on the floor of the ocean. Then later, the pipeline is laid in the open previously laid trench. Another common method of installing a pipeline underwater comprises the laying of the pipeline on the ocean floor and subsequently excavating a trench beneath the pipe by using a high pressure water jet sled. Many attempts at solving the problems involved in the laying of marine pipelines have been devised, as shown in the Schrom U.S. Pat. No. 3,401,473; Hale et al U.S. Pat. No. 3,333,432; Spearman U.S. Pat. No. 3,952,532; Suzuki et al U.S. Pat. No. 4,011,727; Carlsson et al U.S. Pat. No. 4,129,992; Ezoe et al U.S. Pat. No. 3,898,852; Shiroyama et al U.S. Pat. No. 3,824,789; Holberg U.S. Pat. No. 3,788,085; Sherrod U.S. Pat. No. 3,540,266; Sherrod U.S. Pat. No. 3,347,054; Moore U.S. Pat. No. 3,217,499; Lawton U.S. Pat. No. 2,142,136; Lawson et al U.S. Pat. No. 2,067,717; Change et al U.S. Pat. No. 4,112,695; Gunn U.S. Pat. No. 4,091,629; deBoer et al U.S. Pat. No. 4,037,422; Good et al U.S. Pat. No. 3,786,642; Tesson U.S. Pat. No. 3.372.461; Lang al U.S. Pat. No. 3,982,402; and the Uyeda et al U.S. Pat. No. 4,260,287. These devices have certain disadvantages, however, in that most of them require the laying of the pipe and the dredging of the trench therefor be accomplished in separate operations, which is both expensive and time consuming.